Merge topic 'clang-gnulike-support'

74829f01b1 Help: Add notes for topic 'clang-gnulike-support'
19669abe1d Tests: handle string escaping differences with NMake+clang
a2a90f41e3 Tests: require C++14 for the Tutorial
4819ff9647 Tests: fix failures with gnu mode clang on windows
26af0b25e7 cmake: use correct stack size with gnu mode clang on windows
d44c0db0b2 clang: setup correct configuration in gnu mode
b7d5ef23e9 cmGlobalNinjaGenerator: use gnu compatible paths with clang in gnu mode
3d0210d8dc binutils: add the llvm-* variants to the tool lists.
...

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Francesco Bertolaccini <francesco@bertolaccini.dev>
Acked-by: Stanislav Ershov <digital.stream.of.mind@gmail.com>
Acked-by: Saleem Abdulrasool <compnerd@compnerd.org>
Merge-request: !2992

8 files changed, 169 insertions, 50 deletions

diff --git a/Modules/CMakeCCompiler.cmake.in b/Modules/CMakeCCompiler.cmake.in
index f473b0d..9b8d423 100644
--- a/Modules/CMakeCCompiler.cmake.in
+++ b/Modules/CMakeCCompiler.cmake.in
@@ -12,6 +12,7 @@ set(CMAKE_C11_COMPILE_FEATURES "@CMAKE_C11_COMPILE_FEATURES@")
 
 set(CMAKE_C_PLATFORM_ID "@CMAKE_C_PLATFORM_ID@")
 set(CMAKE_C_SIMULATE_ID "@CMAKE_C_SIMULATE_ID@")
+set(CMAKE_C_COMPILER_FRONTEND_VARIANT "@CMAKE_C_COMPILER_FRONTEND_VARIANT@")
 set(CMAKE_C_SIMULATE_VERSION "@CMAKE_C_SIMULATE_VERSION@")
 @_SET_CMAKE_C_COMPILER_ARCHITECTURE_ID@
 @SET_MSVC_C_ARCHITECTURE_ID@
diff --git a/Modules/CMakeCXXCompiler.cmake.in b/Modules/CMakeCXXCompiler.cmake.in
index a1be02b..e7f0e70 100644
--- a/Modules/CMakeCXXCompiler.cmake.in
+++ b/Modules/CMakeCXXCompiler.cmake.in
@@ -14,6 +14,7 @@ set(CMAKE_CXX20_COMPILE_FEATURES "@CMAKE_CXX20_COMPILE_FEATURES@")
 
 set(CMAKE_CXX_PLATFORM_ID "@CMAKE_CXX_PLATFORM_ID@")
 set(CMAKE_CXX_SIMULATE_ID "@CMAKE_CXX_SIMULATE_ID@")
+set(CMAKE_CXX_COMPILER_FRONTEND_VARIANT "@CMAKE_CXX_COMPILER_FRONTEND_VARIANT@")
 set(CMAKE_CXX_SIMULATE_VERSION "@CMAKE_CXX_SIMULATE_VERSION@")
 @_SET_CMAKE_CXX_COMPILER_ARCHITECTURE_ID@
 @SET_MSVC_CXX_ARCHITECTURE_ID@
diff --git a/Modules/CMakeDetermineCCompiler.cmake b/Modules/CMakeDetermineCCompiler.cmake
index 495d7e8..8be781a 100644
--- a/Modules/CMakeDetermineCCompiler.cmake
+++ b/Modules/CMakeDetermineCCompiler.cmake
@@ -114,7 +114,6 @@ if(NOT CMAKE_C_COMPILER_ID_RUN)
 
   include(${CMAKE_ROOT}/Modules/CMakeDetermineCompilerId.cmake)
   CMAKE_DETERMINE_COMPILER_ID(C CFLAGS CMakeCCompilerId.c)
-  CMAKE_DIAGNOSE_UNSUPPORTED_CLANG(C CC)
 
   # Set old compiler and platform id variables.
   if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
diff --git a/Modules/CMakeDetermineCXXCompiler.cmake b/Modules/CMakeDetermineCXXCompiler.cmake
index afcd956..00ef5b9 100644
--- a/Modules/CMakeDetermineCXXCompiler.cmake
+++ b/Modules/CMakeDetermineCXXCompiler.cmake
@@ -109,7 +109,6 @@ if(NOT CMAKE_CXX_COMPILER_ID_RUN)
 
   include(${CMAKE_ROOT}/Modules/CMakeDetermineCompilerId.cmake)
   CMAKE_DETERMINE_COMPILER_ID(CXX CXXFLAGS CMakeCXXCompilerId.cpp)
-  CMAKE_DIAGNOSE_UNSUPPORTED_CLANG(CXX CXX)
 
   # Set old compiler and platform id variables.
   if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
diff --git a/Modules/CMakeDetermineCompilerId.cmake b/Modules/CMakeDetermineCompilerId.cmake
index c7e5685..6083358 100644
--- a/Modules/CMakeDetermineCompilerId.cmake
+++ b/Modules/CMakeDetermineCompilerId.cmake
@@ -136,6 +136,31 @@ function(CMAKE_DETERMINE_COMPILER_ID lang flagvar src)
     set(CMAKE_${lang}_CL_SHOWINCLUDES_PREFIX "")
   endif()
 
+  set(_variant "")
+  if("x${CMAKE_${lang}_COMPILER_ID}" STREQUAL "xClang")
+    if(CMAKE_HOST_WIN32 AND "x${CMAKE_${lang}_SIMULATE_ID}" STREQUAL "xMSVC")
+      if(CMAKE_GENERATOR MATCHES "Visual Studio")
+        set(CMAKE_${lang}_COMPILER_FRONTEND_VARIANT "MSVC")
+      else()
+        # Test whether an MSVC-like command-line option works.
+        execute_process(COMMAND "${CMAKE_${lang}_COMPILER}" -?
+          RESULT_VARIABLE _clang_result
+          OUTPUT_VARIABLE _clang_stdout
+          ERROR_VARIABLE _clang_stderr)
+        if(_clang_result EQUAL 0)
+          set(CMAKE_${lang}_COMPILER_FRONTEND_VARIANT "MSVC")
+        else()
+          set(CMAKE_${lang}_COMPILER_FRONTEND_VARIANT "GNU")
+        endif()
+      endif()
+      set(_variant " with ${CMAKE_${lang}_COMPILER_FRONTEND_VARIANT}-like command-line")
+    else()
+      set(CMAKE_${lang}_COMPILER_FRONTEND_VARIANT "GNU")
+    endif()
+  else()
+    set(CMAKE_${lang}_COMPILER_FRONTEND_VARIANT "")
+  endif()
+
   # Display the final identification result.
   if(CMAKE_${lang}_COMPILER_ID)
     if(CMAKE_${lang}_COMPILER_VERSION)
@@ -149,9 +174,10 @@ function(CMAKE_DETERMINE_COMPILER_ID lang flagvar src)
       set(_archid "")
     endif()
     message(STATUS "The ${lang} compiler identification is "
-      "${CMAKE_${lang}_COMPILER_ID}${_archid}${_version}")
+      "${CMAKE_${lang}_COMPILER_ID}${_archid}${_version}${_variant}")
     unset(_archid)
     unset(_version)
+    unset(_variant)
   else()
     message(STATUS "The ${lang} compiler identification is unknown")
   endif()
@@ -163,6 +189,7 @@ function(CMAKE_DETERMINE_COMPILER_ID lang flagvar src)
     PARENT_SCOPE)
   set(CMAKE_${lang}_XCODE_ARCHS "${CMAKE_${lang}_XCODE_ARCHS}" PARENT_SCOPE)
   set(CMAKE_${lang}_CL_SHOWINCLUDES_PREFIX "${CMAKE_${lang}_CL_SHOWINCLUDES_PREFIX}" PARENT_SCOPE)
+  set(CMAKE_${lang}_COMPILER_FRONTEND_VARIANT "${CMAKE_${lang}_COMPILER_FRONTEND_VARIANT}" PARENT_SCOPE)
   set(CMAKE_${lang}_COMPILER_VERSION "${CMAKE_${lang}_COMPILER_VERSION}" PARENT_SCOPE)
   set(CMAKE_${lang}_COMPILER_VERSION_INTERNAL "${CMAKE_${lang}_COMPILER_VERSION_INTERNAL}" PARENT_SCOPE)
   set(CMAKE_${lang}_COMPILER_WRAPPER "${CMAKE_${lang}_COMPILER_WRAPPER}" PARENT_SCOPE)
@@ -864,38 +891,3 @@ function(CMAKE_DETERMINE_MSVC_SHOWINCLUDES_PREFIX lang userflags)
     set(CMAKE_${lang}_CL_SHOWINCLUDES_PREFIX "" PARENT_SCOPE)
   endif()
 endfunction()
-
-function(CMAKE_DIAGNOSE_UNSUPPORTED_CLANG lang envvar)
-  if(NOT CMAKE_HOST_WIN32 OR CMAKE_GENERATOR MATCHES "Visual Studio" OR
-      NOT "${CMAKE_${lang}_COMPILER_ID};${CMAKE_${lang}_SIMULATE_ID}" STREQUAL "Clang;MSVC")
-    return()
-  endif()
-
-  # Test whether an MSVC-like command-line option works.
-  execute_process(COMMAND "${CMAKE_${lang}_COMPILER}" -?
-    RESULT_VARIABLE _clang_result
-    OUTPUT_VARIABLE _clang_stdout
-    ERROR_VARIABLE _clang_stderr)
-  if(_clang_result EQUAL 0)
-    return()
-  endif()
-
-  # Help the user configure the environment to use the MSVC-like Clang.
-  string(CONCAT _msg
-    "The Clang compiler tool\n"
-    "  \"${CMAKE_${lang}_COMPILER}\"\n"
-    "targets the MSVC ABI but has a GNU-like command-line interface.  "
-    "This is not supported.  "
-    "Use 'clang-cl' instead, e.g. by setting '${envvar}=clang-cl' in the environment."
-    )
-  execute_process(COMMAND rc -help
-    RESULT_VARIABLE _rc_result
-    OUTPUT_VARIABLE _rc_stdout
-    ERROR_VARIABLE _rc_stderr)
-  if(NOT _rc_result EQUAL 0)
-    string(APPEND _msg "  "
-      "Furthermore, use the MSVC command-line environment."
-      )
-  endif()
-  message(FATAL_ERROR "${_msg}")
-endfunction()
diff --git a/Modules/CMakeFindBinUtils.cmake b/Modules/CMakeFindBinUtils.cmake
index 35f75c9..0e84116 100644
--- a/Modules/CMakeFindBinUtils.cmake
+++ b/Modules/CMakeFindBinUtils.cmake
@@ -60,7 +60,9 @@ __resolve_tool_path(CMAKE_MT     "${_CMAKE_TOOLCHAIN_LOCATION}" "Default Manifes
 set(_CMAKE_TOOL_VARS "")
 
 # if it's the MS C/CXX compiler, search for link
-if("x${CMAKE_${_CMAKE_PROCESSING_LANGUAGE}_SIMULATE_ID}" STREQUAL "xMSVC"
+if(("x${CMAKE_${_CMAKE_PROCESSING_LANGUAGE}_SIMULATE_ID}" STREQUAL "xMSVC" AND
+   ("x${CMAKE_${_CMAKE_PROCESSING_LANGUAGE}_COMPILER_FRONTEND_VARIANT}" STREQUAL "xMSVC"
+    OR NOT "x${CMAKE_${_CMAKE_PROCESSING_LANGUAGE}_COMPILER_ID}" STREQUAL "xClang"))
    OR "x${CMAKE_${_CMAKE_PROCESSING_LANGUAGE}_COMPILER_ID}" STREQUAL "xMSVC"
    OR (CMAKE_HOST_WIN32 AND "x${CMAKE_${_CMAKE_PROCESSING_LANGUAGE}_COMPILER_ID}" STREQUAL "xPGI")
    OR (CMAKE_HOST_WIN32 AND "x${CMAKE_${_CMAKE_PROCESSING_LANGUAGE}_COMPILER_ID}" STREQUAL "xNVIDIA")
@@ -80,17 +82,26 @@ else()
   if(CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN)
     set(_CMAKE_TOOLCHAIN_LOCATION ${_CMAKE_TOOLCHAIN_LOCATION} ${CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN}/bin)
   endif()
-  find_program(CMAKE_AR NAMES ${_CMAKE_TOOLCHAIN_PREFIX}ar${_CMAKE_TOOLCHAIN_SUFFIX} HINTS ${_CMAKE_TOOLCHAIN_LOCATION})
 
-  find_program(CMAKE_RANLIB NAMES ${_CMAKE_TOOLCHAIN_PREFIX}ranlib HINTS ${_CMAKE_TOOLCHAIN_LOCATION})
+  if("${CMAKE_${_CMAKE_PROCESSING_LANGUAGE}_COMPILER_ID}" STREQUAL Clang)
+    set(LLVM_OBJDUMP "llvm-objdump")
+    set(LLVM_LLD "ld.lld")
+    set(LLVM_RANLIB "llvm-ranlib")
+    set(LLVM_AR "llvm-ar")
+  endif()
+
+  find_program(CMAKE_AR NAMES ${_CMAKE_TOOLCHAIN_PREFIX}ar${_CMAKE_TOOLCHAIN_SUFFIX} ${LLVM_AR} HINTS ${_CMAKE_TOOLCHAIN_LOCATION})
+
+  find_program(CMAKE_RANLIB NAMES ${_CMAKE_TOOLCHAIN_PREFIX}ranlib ${LLVM_RANLIB} HINTS ${_CMAKE_TOOLCHAIN_LOCATION})
   if(NOT CMAKE_RANLIB)
     set(CMAKE_RANLIB : CACHE INTERNAL "noop for ranlib")
   endif()
 
+
   find_program(CMAKE_STRIP NAMES ${_CMAKE_TOOLCHAIN_PREFIX}strip${_CMAKE_TOOLCHAIN_SUFFIX} HINTS ${_CMAKE_TOOLCHAIN_LOCATION})
-  find_program(CMAKE_LINKER NAMES ${_CMAKE_TOOLCHAIN_PREFIX}ld HINTS ${_CMAKE_TOOLCHAIN_LOCATION})
+  find_program(CMAKE_LINKER NAMES ${_CMAKE_TOOLCHAIN_PREFIX}ld ${LLVM_LLD} HINTS ${_CMAKE_TOOLCHAIN_LOCATION})
   find_program(CMAKE_NM NAMES ${_CMAKE_TOOLCHAIN_PREFIX}nm HINTS ${_CMAKE_TOOLCHAIN_LOCATION})
-  find_program(CMAKE_OBJDUMP NAMES ${_CMAKE_TOOLCHAIN_PREFIX}objdump HINTS ${_CMAKE_TOOLCHAIN_LOCATION})
+  find_program(CMAKE_OBJDUMP NAMES ${_CMAKE_TOOLCHAIN_PREFIX}objdump ${LLVM_OBJDUMP} HINTS ${_CMAKE_TOOLCHAIN_LOCATION})
   find_program(CMAKE_OBJCOPY NAMES ${_CMAKE_TOOLCHAIN_PREFIX}objcopy HINTS ${_CMAKE_TOOLCHAIN_LOCATION})
 
   list(APPEND _CMAKE_TOOL_VARS CMAKE_AR CMAKE_RANLIB CMAKE_STRIP CMAKE_LINKER CMAKE_NM CMAKE_OBJDUMP CMAKE_OBJCOPY)
diff --git a/Modules/Compiler/Clang-CXX.cmake b/Modules/Compiler/Clang-CXX.cmake
index c116078..17f3917 100644
--- a/Modules/Compiler/Clang-CXX.cmake
+++ b/Modules/Compiler/Clang-CXX.cmake
@@ -1,7 +1,7 @@
 include(Compiler/Clang)
 __compiler_clang(CXX)
 
-if(NOT "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
+if("x${CMAKE_CXX_COMPILER_FRONTEND_VARIANT}" STREQUAL "xGNU")
   set(CMAKE_CXX_COMPILE_OPTIONS_VISIBILITY_INLINES_HIDDEN "-fvisibility-inlines-hidden")
 endif()
 
@@ -10,7 +10,8 @@ if(APPLE AND NOT appleClangPolicy STREQUAL NEW)
   return()
 endif()
 
-if(NOT "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
+
+if("x${CMAKE_CXX_COMPILER_FRONTEND_VARIANT}" STREQUAL "xGNU")
   if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 2.1)
     set(CMAKE_CXX98_STANDARD_COMPILE_OPTION "-std=c++98")
     set(CMAKE_CXX98_EXTENSION_COMPILE_OPTION "-std=gnu++98")
@@ -56,6 +57,14 @@ if(NOT "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
 
   unset(_clang_version_std17)
 
+  if("x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
+    # This clang++ is missing some features because of MSVC compatibility.
+    unset(CMAKE_CXX11_STANDARD__HAS_FULL_SUPPORT)
+    unset(CMAKE_CXX14_STANDARD__HAS_FULL_SUPPORT)
+    unset(CMAKE_CXX17_STANDARD__HAS_FULL_SUPPORT)
+    unset(CMAKE_CXX20_STANDARD__HAS_FULL_SUPPORT)
+  endif()
+
   __compiler_check_default_language_standard(CXX 2.1 98)
 elseif(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 3.9
     AND CMAKE_CXX_SIMULATE_VERSION VERSION_GREATER_EQUAL 19.0)
diff --git a/Modules/Platform/Windows-Clang.cmake b/Modules/Platform/Windows-Clang.cmake
index 007ae53..b317da6 100644
--- a/Modules/Platform/Windows-Clang.cmake
+++ b/Modules/Platform/Windows-Clang.cmake
@@ -8,13 +8,120 @@ if(__WINDOWS_CLANG)
 endif()
 set(__WINDOWS_CLANG 1)
 
+macro(__windows_compiler_clang_gnu lang)
+  set(CMAKE_LIBRARY_PATH_FLAG "-L")
+  set(CMAKE_LINK_LIBRARY_FLAG "-l")
+
+  set(CMAKE_IMPORT_LIBRARY_PREFIX "")
+  set(CMAKE_SHARED_LIBRARY_PREFIX "")
+  set(CMAKE_SHARED_MODULE_PREFIX  "")
+  set(CMAKE_STATIC_LIBRARY_PREFIX "")
+  set(CMAKE_EXECUTABLE_SUFFIX     ".exe")
+  set(CMAKE_IMPORT_LIBRARY_SUFFIX ".lib")
+  set(CMAKE_SHARED_LIBRARY_SUFFIX ".dll")
+  set(CMAKE_SHARED_MODULE_SUFFIX  ".dll")
+  set(CMAKE_STATIC_LIBRARY_SUFFIX ".lib")
+  set(CMAKE_DEPFILE_FLAGS_${lang} "-MD -MT <OBJECT> -MF <DEPFILE>")
+
+  set(CMAKE_FIND_LIBRARY_PREFIXES "lib" "")
+  set(CMAKE_FIND_LIBRARY_SUFFIXES ".dll" ".dll.a" ".a" ".lib")
+  set(CMAKE_SUPPORT_WINDOWS_EXPORT_ALL_SYMBOLS 1)
+  set (CMAKE_LINK_DEF_FILE_FLAG "-Xlinker /DEF:")
+
+  if("${CMAKE_${lang}_SIMULATE_VERSION}" MATCHES "^([0-9]+)\\.([0-9]+)")
+    math(EXPR MSVC_VERSION "${CMAKE_MATCH_1}*100 + ${CMAKE_MATCH_2}")
+  endif()
+
+  # No -fPIC on Windows
+  set(CMAKE_${lang}_COMPILE_OPTIONS_PIC "")
+  set(CMAKE_${lang}_COMPILE_OPTIONS_PIE "")
+  set(_CMAKE_${lang}_PIE_MAY_BE_SUPPORTED_BY_LINKER NO)
+  set(CMAKE_${lang}_LINK_OPTIONS_PIE "")
+  set(CMAKE_${lang}_LINK_OPTIONS_NO_PIE "")
+  set(CMAKE_SHARED_LIBRARY_${lang}_FLAGS "")
+
+  set(CMAKE_${lang}_USE_RESPONSE_FILE_FOR_OBJECTS 1)
+  set(CMAKE_${lang}_USE_RESPONSE_FILE_FOR_LIBRARIES 1)
+  set(CMAKE_${lang}_USE_RESPONSE_FILE_FOR_INCLUDES 1)
+
+  # Create archiving rules to support large object file lists for static libraries.
+  set(CMAKE_${lang}_ARCHIVE_CREATE "<CMAKE_AR> qc <TARGET> <LINK_FLAGS> <OBJECTS>")
+  set(CMAKE_${lang}_ARCHIVE_APPEND "<CMAKE_AR> q  <TARGET> <LINK_FLAGS> <OBJECTS>")
+  set(CMAKE_${lang}_ARCHIVE_FINISH "<CMAKE_RANLIB> <TARGET>")
+  set(CMAKE_${lang}_CREATE_SHARED_LIBRARY
+    "<CMAKE_${lang}_COMPILER> -nostartfiles -nostdlib <CMAKE_SHARED_LIBRARY_${lang}_FLAGS> <LANGUAGE_COMPILE_FLAGS> <LINK_FLAGS> <CMAKE_SHARED_LIBRARY_CREATE_${lang}_FLAGS> -o <TARGET> ${CMAKE_GNULD_IMAGE_VERSION} -Xlinker /implib:<TARGET_IMPLIB> -Xlinker /pdb:<TARGET_PDB> -Xlinker /version:<TARGET_VERSION_MAJOR>.<TARGET_VERSION_MINOR> <OBJECTS> <LINK_LIBRARIES>")
+  set(CMAKE_${lang}_CREATE_SHARED_MODULE ${CMAKE_${lang}_CREATE_SHARED_LIBRARY})
+  set(CMAKE_${lang}_LINK_EXECUTABLE
+    "<CMAKE_${lang}_COMPILER> -nostartfiles -nostdlib <FLAGS> <CMAKE_${lang}_LINK_FLAGS> <LINK_FLAGS> <OBJECTS>  -o <TARGET> -Xlinker /implib:<TARGET_IMPLIB> -Xlinker /pdb:<TARGET_PDB> -Xlinker /version:<TARGET_VERSION_MAJOR>.<TARGET_VERSION_MINOR> ${CMAKE_GNULD_IMAGE_VERSION} <LINK_LIBRARIES>")
+
+  set(CMAKE_${lang}_COMPILE_OPTIONS_MSVC_RUNTIME_LIBRARY_MultiThreaded         -Xclang -flto-visibility-public-std -D_MT -Xclang --dependent-lib=libcmt)
+  set(CMAKE_${lang}_COMPILE_OPTIONS_MSVC_RUNTIME_LIBRARY_MultiThreadedDLL      -D_DLL -D_MT -Xclang --dependent-lib=msvcrt)
+  set(CMAKE_${lang}_COMPILE_OPTIONS_MSVC_RUNTIME_LIBRARY_MultiThreadedDebug    -D_DEBUG -Xclang -flto-visibility-public-std -D_MT -Xclang --dependent-lib=libcmtd)
+  set(CMAKE_${lang}_COMPILE_OPTIONS_MSVC_RUNTIME_LIBRARY_MultiThreadedDebugDLL -D_DEBUG -D_DLL -D_MT -Xclang --dependent-lib=msvcrtd)
+
+  if(CMAKE_MSVC_RUNTIME_LIBRARY_DEFAULT)
+    set(__ADDED_FLAGS "")
+    set(__ADDED_FLAGS_DEBUG "")
+  else()
+    set(__ADDED_FLAGS_DEBUG "-D_DEBUG -D_DLL -D_MT -Xclang --dependent-lib=msvcrtd")
+    set(__ADDED_FLAGS "-D_DLL -D_MT -Xclang --dependent-lib=msvcrt")
+  endif()
+
+  string(APPEND CMAKE_${lang}_FLAGS_DEBUG_INIT " -g -Xclang -gcodeview -O0 ${__ADDED_FLAGS_DEBUG}")
+  string(APPEND CMAKE_${lang}_FLAGS_MINSIZEREL_INIT " -Os -DNDEBUG ${__ADDED_FLAGS}")
+  string(APPEND CMAKE_${lang}_FLAGS_RELEASE_INIT " -O3 -DNDEBUG ${__ADDED_FLAGS}")
+  string(APPEND CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT " -O2 -g -DNDEBUG -Xclang -gcodeview ${__ADDED_FLAGS}")
+  set(CMAKE_INCLUDE_SYSTEM_FLAG_${lang} "-isystem ")
+
+  unset(__ADDED_FLAGS)
+  unset(__ADDED_FLAGS_DEBUG)
+  string(TOLOWER "${CMAKE_BUILD_TYPE}" BUILD_TYPE_LOWER)
+  set(CMAKE_${lang}_STANDARD_LIBRARIES_INIT "-lkernel32 -luser32 -lgdi32 -lwinspool -lshell32 -lole32 -loleaut32 -luuid -lcomdlg32 -ladvapi32 -loldnames")
+
+  enable_language(RC)
+endmacro()
+
 if("x${CMAKE_C_SIMULATE_ID}" STREQUAL "xMSVC"
     OR "x${CMAKE_CXX_SIMULATE_ID}" STREQUAL "xMSVC")
-  include(Platform/Windows-MSVC)
-  macro(__windows_compiler_clang lang)
-    set(_COMPILE_${lang} "${_COMPILE_${lang}_MSVC}")
-    __windows_compiler_msvc(${lang})
-  endmacro()
+
+  if ( DEFINED CMAKE_C_COMPILER_ID AND DEFINED CMAKE_CXX_COMPILER_ID
+       AND NOT "x${CMAKE_C_COMPILER_ID}" STREQUAL "x${CMAKE_CXX_COMPILER_ID}")
+    message(FATAL_ERROR "The current configuration mixes Clang and MSVC or "
+            "some other CL compatible compiler tool. This is not supported. "
+            "Use either clang or MSVC as both C and C++ compilers.")
+  endif()
+
+  if ( DEFINED CMAKE_C_COMPILER_FRONTEND_VARIANT AND DEFINED CMAKE_CXX_COMPILER_FRONTEND_VARIANT
+       AND NOT "x${CMAKE_C_COMPILER_FRONTEND_VARIANT}" STREQUAL "x${CMAKE_CXX_COMPILER_FRONTEND_VARIANT}")
+    message(FATAL_ERROR "The current configuration uses the Clang compiler "
+            "tool with mixed frontend variants, both the GNU and in MSVC CL "
+            "like variants. This is not supported. Use either clang/clang++ "
+            "or clang-cl as both C and C++ compilers.")
+  endif()
+
+  if ( "x${CMAKE_CXX_COMPILER_FRONTEND_VARIANT}" STREQUAL "xMSVC" OR "x${CMAKE_C_COMPILER_FRONTEND_VARIANT}" STREQUAL "xMSVC" )
+    include(Platform/Windows-MSVC)
+
+    macro(__windows_compiler_clang lang)
+      set(_COMPILE_${lang} "${_COMPILE_${lang}_MSVC}")
+      __windows_compiler_msvc(${lang})
+    endmacro()
+  else()
+    cmake_policy(GET CMP0091 __WINDOWS_CLANG_CMP0091)
+    if(__WINDOWS_CLANG_CMP0091 STREQUAL "NEW")
+      set(CMAKE_MSVC_RUNTIME_LIBRARY_DEFAULT "MultiThreaded$<$<CONFIG:Debug>:Debug>DLL")
+    else()
+      set(CMAKE_MSVC_RUNTIME_LIBRARY_DEFAULT "")
+    endif()
+    unset(__WINDOWS_CLANG_CMP0091)
+
+    set(CMAKE_BUILD_TYPE_INIT Debug)
+
+    macro(__windows_compiler_clang lang)
+      __windows_compiler_clang_gnu(${lang})
+    endmacro()
+  endif()
+
 else()
   include(Platform/Windows-GNU)
   macro(__windows_compiler_clang lang)